Wall Street had its worst week in four years, and it ended particularly badly on Friday, when the Dow Jones industrial average closed down 530 points. This was the ninth-biggest point decline in its history.

Investors were reportedly worried about signs of a slowdown in the Chinese economy. The stock of Apple, which depends heavily on Chinese demand, fell more than 6 percent.

The Dow finished at 16,459, falling more than 1,000 points last week alone. Its decline for the day on Friday reached 3.1 percent. The Standard & Poor's 500 index finished down 3.2 percent.